This disclosure relates to a method for providing localized heating in an oil well at precise depths to accomplish or expedite specific objectives. The disclosure also relates to the use of a heating tool which can be lowered into an oil well to apply heat at a precise depth to achieve a desired result. The specific objectives may include localized heating of a fresh cement slurry or other sealant having a similar purpose to accelerate curing, or localized heating of recently emplaced chemicals which are formulated to be thermally activated. One purpose of such chemicals is to viscosify or increase in gel strength after being pumped into an oil well production zone, in order to restrict the production of unwanted formation fluids such as water.
Current techniques for cementing steel or other casing in a borehole during oil well construction involve emplacing a fluid cement slurry between the casing and the borehole, after which the cement slurry is allowed to set up or cure to become hard as rock. The cement provides a bond between the casing and the surrounding rock formation. The curing of the cement requires a waiting period which necessarily increases the total time required to construct the well. It is commonly known that the time required for the curing process decreases if the temperature of the cement slurry is increased. Also, to minimize construction cost it is preferred to minimize the time required for the cement to cure. Currently, any heating to accelerate the curing of the cement slurry is provided by the natural surrounding environment as well as the heat generated by the exothermic reactions involved in the cement curing process. Accordingly, it would be desirable to provide a tool to effect an increase in cement slurry temperature to accelerate the curing of the cement slurry.
During the production phase of an oil or gas well, some amount of water may also be produced, which is usually not desirable since the water has no market value. In some wells, the fraction of water produced, relative to the desired fluids, is so great that it impairs well profitability, such that conformance treatments, also known as water shut-off treatments, are performed on the well. Conformance chemicals are fluids designed to react or interact with formation rock and/or formation fluids in such manner that they reduce or eliminate the rate at which water is produced. It would be desirable to emplace such conformance chemicals at particular depth locations at or near the rock formations from which oil and/or gas is produced and then to thermally activate such conformance chemicals.
Downhole heating tools used to provide localized heat at perforation locations in producing oil wells. The heating tool increases the temperature of the produced oil which results in an increase in flow rate through the perforations due to a consequent decrease in viscosity of the produced oil.
Therefore, what is needed is a heating tool and a method for using a heating tool to reduce the curing time of a cement slurry or other sealant having a similar purpose and to heat conformance chemicals that are designed to be thermally activated.